1. Field of the Invention
The present invention relates to an imaging optical system, and more particularly, to a subminiature imaging optical system mounted on a mobile communication terminal, personal digital assistant (PDA) and the like or used in a surveillance camera, a digital camera and the like.
2. Description of the Related Art
In general, mobile communication terminals had only functions of basic communication at their incipient stage. However, with increased use, the mobile communication terminals are required to have diversified functions ranging from photographing to image transmission and video communication, continuously evolving in their functions and services. Recently, a new expanded concept of mobile communication terminal by integrating digital camera technology with mobile phone technology, i.e., so called camera phones or camera mobile phones are significantly attracting attention.
In particular, the imaging optical system mounted on the camera phone is not only required to be miniaturized, lightweight and low cost, but also have high resolution since the pixel size of an image sensor formed of a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) used in the imaging optical system is decreasing.
In order to satisfy miniaturization and low cost, the imaging optical system mounted on a small device such as a mobile phone needs to have a small number of lenses as possible, but this restricts a degree of freedom in designing and undermines the optical capabilities.
Therefore, there is required a subminiature imaging optical system which is easily miniaturized while having high resolution and excellent aberrational characteristics.